JP2023528824A - Tunable nanocircuit and waveguide systems and methods on optical fibers - Google Patents

Abstract

The present disclosure provides devices, systems, circuits, and effective methods for advanced optical applications using plasmonics and ENZ materials. The present disclosure provides optical tunability of propagating plasmon phase and amplitude, nonlinear optical effects, and enhanced resonant networks in fiber-tipped nanocircuits, integrating tunable plasmonic and ENZ effects for in-fiber applications to provide optical fibers with high speed operation and low power consumption. The present invention enables efficient coupling of plasmonic functional nanocircuits onto the facets of an optical fiber core. The present invention can also use gate-tunable ENZ materials to electrically and nonlinearly optically tune plasmonic nanocircuits to achieve advanced optical manipulations. The present invention efficiently integrates and manipulates voltage-tuned ENZ resonances for phase and amplitude modulation of fiber optic nanocircuits.

Description

STATEMENT ON FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT Not Applicable

Reference N/A

The present disclosure relates generally to optical fibers. More specifically, the present disclosure relates to optical fibers and plasmonics, and related devices, circuits, and methods.

Optical fibers are well known as a representative means of directing and manipulating light. Optical fibers are widely used in various applications such as long-distance optical communication, light generation with fiber lasers, remote and optical sensing, fiber imaging in endoscopes, and fiber laser surgery. The increased use of optical technology to improve computing and communication technology has resulted in new innovative fabrication and integration of devices involving combinations of different elements and novel chemical compounds. One area uses plasmonics to achieve the dual goal of achieving optical speed without sacrificing the miniaturization of electronic circuits. Plasmonics can take advantage of the different properties of light and electrons, such as wave propagation properties, to achieve effects that are not possible in particle-oriented applications. Developing components such as switches and other types of devices that take advantage of the property of light to excite electrons to generate plasmons is an important step towards making practical plasmonic circuits.

On-chip photonic devices and circuits are being developed due to the constant demand for high-speed transmission of optical signals and miniaturization of devices. However, due to the diffraction limit, dielectric photonic devices cannot be shrunk to sizes comparable to the semiconductor components found in computer processors. On the other hand, electronic interconnects within the processor are speed limited due to thermal and resistance-capacitance (RC) delay time issues. "Photonic" approaches, such as silicon photonics, are among the promising solutions for chip-to-chip and on-chip interconnections, as photonics offer high-bandwidth data transmission, low power consumption, and crosstalk-free communication. be. However, it is an obstacle that the size of photonic devices is severely limited by diffraction, i.e., optical waveguides with dimensions smaller than half the wavelength cannot guide light, and nanometer-scale photonics cannot Circuit development is severely restricted.

Plasmonics offers a different approach to nanoscale lightwave processing, achieving sub-diffraction-limited light guidance while maintaining high optical bandwidth. Surface plasmon polaritons (plasmonic waves) are electromagnetic waves propagating along interfaces between metals and dielectric media in nanoscale optical confinement well below the diffraction limit of light. Various plasmonic waveguides and devices have been implemented to construct chip-based plasmonic systems, such as plasmonic stripe, wedge, slot or nanowire waveguides, splitters and multiplexers, interconnects.

However, to date there is no simple and efficient means of coupling light from a diffraction-limited waveguide into highly confined modes of plasmonic nanostructures or nanocircuits while preserving photonic functionality. Lenses, processors, free-space transmission, grating and end-fire coupling with scattered light, collection of scattered light, and other steps to obtain efficient optical coupling between plasmonic and optical fiber modes. and several attempts involving components. Their schemes require advanced nanofabrication and optical alignment, and systems demonstrated prior to the present invention do not exhibit versatility. Furthermore, an active version of the plasmonic circuit, with arbitrary control of the phase and amplitude of individual plasmonic waves by external electrical/optical modulation, appears to be a milestone yet to be realized.

Attempts have been made to fabricate plasmonic components in the facets of optical fibers so that the plasmonic elements can interact directly with the fibre. Such attempts generally coat the end of the optical fiber, rather than the waveguide or circuit, with a metal such as gold to support the plasmonic mode. A plasmonic element can directly interact with a well-guided spatial mode pattern in the fiber. Miniature optical components such as diffraction gratings, optical tweezers, and plasmonic sensors have been realized with periodic metallic nanostructures (ie, slits, holes, and bars) on the facets of conventional fibers. However, plasmonic nanostructures on these fibers are limited to the excitation of non-propagating local plasmons, limiting the potential applications of plasmonic optical fibers. Furthermore, many of the reported plasmonic on-fiber devices are passive, so their optical function cannot be altered after fabrication.

Therefore, there is a need to incorporate new materials and new plasmonic nanostructures into optical fibers in order to improve processing and transmission capabilities and enable new functionalities.

The present disclosure provides devices, systems including circuits, and effective methods for designing advanced optical applications using plasmonics and novel epsilon near-zero (ENZ) refractive index material-based optical fiber applications. . The present disclosure provides improved optical tunability of propagating plasmon phases and amplitudes, nonlinear optical effects, and resonant networks in fiber-tipped nanocircuits, and tunable plasmonic effects and tunables for novel in-fiber applications. Integrate ENZ material effects. The integration of optical and electrical functionality with plasmonic nanocircuit design and ENZ material properties extends the functionality of optical fibers with high speed operation and low power consumption. The present invention allows efficient bonding of plasmonic function chips directly onto the facets of an optical fiber core using techniques such as focused ion beam and electron beam lithography. The present invention can also use gate-tunable ENZ materials to electrically and nonlinearly optically tune plasmonic nanostructures and resonant waveguide circuits to achieve advanced optical manipulations. The present invention efficiently integrates and manipulates voltage-tuned ENZ resonances for phase and amplitude modulation in on-fiber nanocircuits. The phase flexibility and functionality of plasmonic structures can enhance in-fiber optical components such as filters and amplifiers, linear polarizers, focusing lenses, and efficient fiber optic tweezers.

The present disclosure provides nanocircuit devices. The nanocircuit device comprises a first optical fiber having a facet and a nanocircuit integrally formed on the facet, the nanocircuit directing light energy from the first optical fiber to the a nanocoupler configured to directly couple plasmonic energy in a nanocircuit; and a nanocoupler formed in said nanocircuit, coupled to said nanocoupler, and configured to conduct plasmonic energy in said nanocircuit. and at least one waveguide.

Additionally, the present disclosure provides methods of fabricating nanocircuit devices. The method comprises providing a faceted optical fiber, depositing a metal layer on the facet, milling grooves in the metal layer on the facet and configured to form a waveguide; milling a nanocoupler into the metal layer on the facet and configured to directly couple optical energy from the optical fiber and plasmon energy in the waveguide.

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

1 is a schematic diagram of one embodiment of a nanocircuit system according to the present invention; FIG. 1 is a schematic illustration of a fabrication process for forming an integrated nanocircuit on a facet (hereinafter also referred to as "tip") of an optical fiber; FIG. 1 is a schematic diagram of an exemplary fiber optic nanocircuit having a slot plasmonic waveguide with an antenna; FIG. 1 is a schematic diagram of an exemplary antenna for coupling an optical fiber mode to a plasmonic slot waveguide mode; FIG. 3B is a schematic diagram of the vertical profile of the plasmonic slot waveguide mode shown in FIG. 3A showing the electric field component of the light in the slot; FIG. SEM image of an exemplary plasmonic slot waveguide nanocircuit on an optical facet. 4B is an enlarged SEM image of the waveguide of FIG. 4A; FIG. 4B is an SEM image of another exemplary plasmonic slot waveguide on an optical facet; FIG. 4D is an enlarged SEM image of the waveguide of FIG. 4C; FIG. 2 is a superimposed optical and SEM image of a waveguide nanocircuit; SEM image of the waveguide and the output at a wavelength of 1550 nm. SEM images of the waveguide and the output at a wavelength of 1630 nm. 4 is a chart showing exemplary coupling efficiencies for a single waveguide in the wavelength range of 1500-1630 nm; SEM images of multi-channel waveguide nanocircuits on optical fibers. 4 is a measured far-field optical image showing four output signals; FIG. 4 is a close-up of a measured far-field optical image near the core and output region of an optical fiber; FIG. 6B is a magnified SEM image of the multi-channel waveguide nanocircuit of FIG. 6A. FIG. 6C is an enlarged SEM image of the multi-channel waveguide nanocircuit of FIG. 6D showing the output antenna ports. 6E is a magnified SEM image of the multi-channel waveguide nanocircuit of FIG. 6E showing the input antenna near the core of the optical fiber. 6B is an SEM image of a multi-channel waveguide nanocircuit similar to that of FIG. 6A formed on a polarization-maintaining photonic crystal fiber (PM-PCF). FIG. 6G is a magnified SEM image of the multi-channel waveguide nanocircuit of FIG. 6G. 6H is a magnified SEM image of the multi-channel waveguide nanocircuit of FIG. 6H showing the input antenna near the core of the optical fiber. SEM images of optical fiber facets before the fabrication of integrated directional coupler nanocircuits. FIG. 4B is a close-up view of the fiber optic facet after the exemplary plasmonic directional coupler has been fabricated. Figure 7C is a further enlarged view of the plasmonic directional coupler of Figure 7B; Measured far-field optical images showing two outputs at 1550 nm. Measured far-field optical images showing two outputs at 1630 nm. FIG. 11 is an SEM image of a panda-type (PS) fiber optic facet with another exemplary integrated directional coupler nanocircuit; FIG. FIG. 7F is a superimposed image of far-field measurements at a wavelength of 1630 nm for the exemplary plasmonic directional coupler of FIG. 7F. 7F is a far-field image of the plasmonic directional coupler of FIG. 7F using a supercontinuum (SC) source laser without optical filters. Far-field optical image measured at a wavelength of 1480 nm detected with cross-polarization to the incident light. Far-field optical image measured at a wavelength of 1550 nm detected with cross-polarization to the incident light. Far-field optical images measured at a wavelength of 1650 nm detected with cross-polarization to the incident light. FIG. 4 is an SEM image of an exemplary polarization splitter nanocircuit; FIG. 8B is an enlarged SEM image of the input antenna of the polarization splitter of FIG. 8A; 8B is a measured far-field optical mirror image of the polarization splitter of FIG. 8A showing horizontal incident polarization transmitted through a waveguide with a horizontally aligned input antenna; FIG. 8B is a measured far-field optical mirror image of the polarization splitter of FIG. 8A showing vertical incident polarization transmitted through a waveguide with a vertically aligned input antenna; FIG. 8B is a chart showing the transmission strength as a function of horizontal or vertical alignment, respectively, with horizontal and vertical polarization inputs for each waveguide shown in the polarization splitter of FIG. 8A; 8B is a chart showing the transmission strength as a function of respective horizontal or vertical alignments with rotationally polarized input not in the horizontal or vertical plane for each waveguide shown in the polarization splitter of FIG. 8A; FIG. 10 is an SEM image of an exemplary resonant waveguide network (RGWN) nanocircuit fabricated on a planar substrate; 4 is a measured optical image of an RGWN with a resonance size of 7.5 μm, showing the output at a wavelength of 1570 nm. FIG. 8C is a measured optical image of the output of the RGWN of FIG. 8B at a wavelength of 1550 nm. Fig. 4 is an SEM image of fabricated RGWNs of different sizes; SEM image of an exemplary embodiment of an ultra-small RGWN nanocircuit with a cavity size of 300 nm. 10B is a measurement optical image of the RGWN of FIG. 10A; FIG. 4B is an SEM image of another exemplary embodiment of an RGWN with a cavity size of 7.5 μm; FIG. 10D is a chart showing exemplary measured and simulated spectra for Port 1 of the RGWN of FIG. 10C; 10D is a chart showing exemplary measured and simulated spectra for port 2 of the RGWN of FIG. 10C; 10D is a chart showing exemplary measured and simulated spectra for port 4 of the RGWN of FIG. 10C; 1 is a schematic diagram of an example of a tunable RGWN nanocircuit; FIG. Fig. 2 is a schematic diagram of a corresponding transparent conducting oxide (TCO) waveguide; FIG. 11 shows a simulated response when bias is applied; Fig. 10 shows a simulation response with no bias applied, demonstrating ultra-fast switching capability; FIG. 2 is a schematic diagram of an exemplary tunable ENZ/plasmonic directional coupler nanocircuit for nonlinear optical switching; 11B is a schematic diagram of an exemplary corresponding TCO waveguide of the directional coupler of FIG. 11A; FIG. Fig. 3 shows a simulated field profile of a low pump power ENZ/plasmonic directional coupler; Fig. 3 shows a simulated field profile of an ENZ/plasmonic directional coupler with high pump power; 1A-1C are schematic diagrams illustrating exemplary embodiments of a tunable optical fiber ENZ nanocircuit having an optical fiber with a single-mode core, a nanocircuit on the tip of the optical fiber, and a multi-core optical fiber. FIG. 10 is a schematic diagram illustrating another exemplary embodiment of a tunable optical fiber ENZ nanocircuit with a single mode core; FIG. 2 is a schematic diagram showing an exemplary tunable fiber optic ENZ nanocircuit with multi-core fibers for providing multiple inputs to the nanocircuit; 1 is a schematic diagram of a fiber optic plasmonic waveguide sensor; FIG. 14B is an enlarged view of the nanostructures of FIG. 14A. FIG. FIG. 3 shows an example of a structure fabricated in an optical fiber with long interaction length;

The above figures and the following descriptions of specific structures and functions are not provided to limit the scope of applicant's invention or the scope of the appended claims. Rather, the figures and written description are provided to teach one of ordinary skill in the art to make and use the invention for which patent protection is sought. Those skilled in the art will appreciate that not all features of a commercial embodiment of the invention have been described or shown for the sake of clarity and understanding. Those skilled in the art will appreciate that the development of an actual commercial embodiment incorporating aspects of the present disclosure requires numerous implementation-specific decisions in order to achieve the developer's ultimate goal for the commercial embodiment. You will also understand that Such implementation-specific decisions may include, but are not limited to, compliance with system-related, business-related, government-related, and other constraints, which may vary by particular implementation or location, or over time. It is what you get. Although the developer effort may be in the absolute sense complex and time consuming, such effort is nevertheless a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. would be It should be understood that the inventions disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. The use of singular terms such as, but not limited to, "a" is not intended to limit the number of items. Moreover, various methods and embodiments of the system can be included in combination with each other to produce variations of the disclosed methods and embodiments. Discussion of singular elements may include plural elements and vice versa. A reference to at least one item may include one or more items. Also, various aspects of the embodiments may be used in combination with each other to achieve the perceived goals of the present disclosure. Unless the context requires otherwise, the terms "comprise" or variations such as "comprising" are intended to include at least the recited element or step or group of elements or steps or equivalents thereof. means and does not exclude larger numerical quantities or other elements or steps or groups of elements or steps or their equivalents. Terms such as "coupling", "coupling", "coupler" are used broadly herein to secure, couple, fasten, attach, join, insert therein, form on or in, communicate with. , or any method or device for otherwise associating, e.g., mechanically, magnetically, electrically, chemically, operatively, directly or with intermediate elements, joining together portions of one or more members and may include, but is not limited to, integrally forming one functional member with another. Coupling may occur in any orientation, including rotation. A device or system may be used in multiple directions and orientations. The order of steps can occur in various orders, unless otherwise specified. Various steps described herein may be combined with other steps, interleaved with described steps, and/or divided into multiple steps. Some elements are named by device name for brevity and will be understood to include systems or sections such that the processor encompasses related component processing systems known to those skilled in the art. , may not be specified. Various structures that perform various functions and are non-limiting in shape, size and description, but serve as exemplary structures that can be varied as would be known to one of ordinary skill in the art given the teachings contained herein. Examples are provided in the description and figures.

In general, the present disclosure provides effective methods for designing advanced optical applications using plasmonics and novel ENZ material-based optical fiber applications. The present invention, in at least one aspect, integrates opto-electronically tunable plasmonic nanocircuits and devices onto optical fiber tips for advanced optical manipulation and communications. The present invention enables efficient bonding of plasmonic function chips directly onto the facets of an optical fiber core by a variety of techniques, including focused ion beam and electron beam lithography techniques. Gating-tunable ENZ materials can also be used to electrically and nonlinearly optically tune plasmonic nanostructures and resonant waveguide circuits to enable advanced optical manipulation.

In the present invention, optical fiber tips can be fabricated with plasmonic nanocircuits for light manipulation. However, previously reported known plasmonic structures are limited to local plasmonics excitation, which limits their capabilities for manipulation of plasmonic waves, resulting in nanostructure-enhanced plasmonic light. Fiber functionality is limited. The present invention can provide high performance plasmonic nanocircuits with tunability to enhance the functionality of plasmonic optical fibers.

FIG. 1 is a schematic diagram of one embodiment of a nanocircuit system according to the present invention. FIG. 1 shows a nanocircuit system 2 having an optical fiber 4 with at least one core 6 with facets 8 . The nanocircuit 10 is formed on an optical fiber facet 8 so that it is integral with the optical fiber for coupling to the facet and the optical fiber 4 provides input energy to the nanocircuit. In at least some embodiments, another optical fiber 12 is coupled to the nanocircuit to receive energy from the nanocircuit and emit energy through one or more output ports 14 in optical fiber 12 . Exemplary nanocircuits 10A-10F are shown in enlarged view of nanocircuit 10. FIG. Non-limiting examples of such include modulators/directors 10A, optical splitters 10B, directional couplers/demultiplexers 10C, waveguide resonators/routers 10D, polarization couplers 10E, and composite structures. 10F can be included. The present disclosure provides tunable nanocircuits that can provide functions such as optical switching, multiplexing/demultiplexing, directional coupling, routing, and resonance/sensing effects. As used herein, the term "nano" is meant to include individual devices down to 1000 nm, more specifically up to several hundred nm. These tunable nanocircuit fiber optic tips can lead to novel communication and optical and/or biological sensing devices. The present disclosure provides complex plasmonic nanocircuits, such as gap plasmonic waveguides, multichannel plasmonic waveguides, plasmonic directional couplers, and resonant waveguide networks, directly on the facets of optical fibers. It is something to do. Nanocircuits can be fabricated on facets using, for example, focused ion beam milling and electron beam lithography techniques. Deposition of materials on the facets uses atomic layer deposition (ALD) techniques to deposit, for example, transparent conductive oxide (TCO) or metal nitride epsilon near-zero (ENZ) materials for plasmonic nanocircuits. can include allowing ENZ materials can be used to efficiently excite gateable ENZ modes in optical fiber circuits. Electrical bias can actively control the plasmonic/ENZ nanostructures on the fiber to achieve multifunctionality. The present disclosure also provides for controlling plasmonic/ENZ hybrid circuits utilizing enhanced ENZ nonlinearity features for efficient nonlinear optical switching and manipulation. The present invention can take advantage of electronic and optical switching functions to design optical networks, as well as routing and functional devices integrated into the ends of optical fibers. Further, the present disclosure provides enhanced quantum and Raman emission effects by exciting emitters/molecules in ENZ modes in conductive oxide/metal nitride active layers with plasmonic/ENZ nanocircuits. The results of the underlying principles taught in this disclosure can be illustrated with some non-limiting examples.

This optimized configuration provides direct coupling from optical fibers to plasmonic nanocircuits without the need for bulky optical components. This capability reduces the need for chip-to-chip and even fiber-to-chip configurations and moves toward coupling these integrated circuits directly onto fiber facets. The present disclosure provides miniature in-fiber devices composed of plasmonic nanocircuits on fiber tips. These devices potentially reduce the complexity of photonic integrated circuits (PICs) (also called “integrated optical circuits”), optical coupling to nanocircuits for signal processing within plasmonic nanocircuits, and A stand-alone optical system is provided that enables optical coupling from nanocircuits. Embodiments provided herein provide fiber facets for unique plasmonic networks on the tip of an optical fiber to illustrate how circuit patterning incorporates miniature optical circuits on fiber. shows the fabrication technology in

FIG. 2 is a schematic illustration of a fabrication process for creating integrated nanocircuits on the facet (also referred to herein as the “tip”) of an optical fiber. For example, polarization-maintaining photonic crystal fibers (PCF) and Panda-type (PS) optical fibers 4 can be used in these nanocircuits. First, the facets 8 are cleaved and a conductive layer 16, such as a metal layer about 200 nm thick, such as a gold layer, is deposited on the fiber using an RF magnetron sputtering machine with a chamber pressure of 10 ⁻³ Torr or a thermal evaporation technique. It can be deposited on the facet. The gold-deposited fiber 4 can be brought into a dual beam focused ion beam scanning electron microscope (FIB-SEM) or other suitable processing system 18 for further processing and fabrication of the nanocircuit 10 . The fiber can be mounted vertically in the holder so that the tip of the fiber is flat on the cross section and the fiber is not tilted. The fiber facets can be arranged such that the center of the core of the fiber correlates to the selected design pattern.

Nanocircuits can be patterned, for example, in conventional Panda-type polarization-maintaining optical fibers. This fiber has two large lobes of high index material surrounding a solid core on either side. Photonic crystal fibers (PCFs), including polarization-maintaining PCFs (PM-PCFs), are also examples. Optical fibers can be milled with a focused ion beam (FIB). E-beam lithography can also be used to fabricate nanostructures with small feature sizes (eg, <100 nm). Ga+ ion currents in FIBs can be used to directly mill nanostructures on optical fibers. An applied voltage of 30 kV and an ion beam current of 10 pA can be used for the fabrication process.

3A-3C are schematic diagrams and electron micrographs for efficiently coupling an optical fiber mode and a plasmonic slot waveguide mode with an antenna. FIG. 3A is a schematic diagram of an exemplary fiber optic nanocircuit with slot plasmonic waveguides. FIG. 3B is a schematic diagram of an exemplary antenna for coupling an optical fiber mode to a plasmonic slot waveguide mode. FIG. 3C is a schematic diagram of the vertical profile of the plasmonic slot waveguide mode shown in FIG. 3A showing the electric field component of the light within the slot. Conductive layer 16 may be milled to form slots 20 in the layer. The antenna 22 shown in FIG. 3B can be used to efficiently couple an electromagnetic signal as light through an optical fiber into a plasmonic slot waveguide to achieve narrow directivity. Although not shown, other nanocouplers such as plasmonic grating couplers, plasmonic waveguide tapers, and nanoparticle couplers can also be used. The antenna can convert modes with high efficiency. Bowtie antennas have been shown to have a coupling efficiency of 10%. The Yagi-Uda antenna has been shown to have a coupling efficiency of 45% and a radiation efficiency of 60% from the slot waveguide to air and substrate, and is commonly used for the exemplary nanocircuits herein. It is The relative dimensions of the fabricated Yagi-Uda antenna can be seen from FIG. 3B, where the gap and waveguide width between the two dipole antenna components are close to the intended design of 80 nm and 300 nm, respectively. This antenna coupling allows the forward-propagating core mode to be directly coupled to the plasmonic nanostructure without the complex prism coupling of the prior art. The coupling efficiencies of silica covered Au waveguides from air and silica can be 15% and 45%, respectively. A component of such an antenna includes two dipole antennas each connected to a plasmonic waveguide slot via a feed element. Behind the dipole antenna is a passive element reflector that further enhances the feeding mechanism to the waveguide. The antenna length can be chosen such that the antenna has maximum coupling efficiency at 1550 nm. In at least one embodiment, fiber core light can be coupled into a plasmonic slot waveguide by fabricating nanocircuits near the core region of the fiber. For symmetrical coupling, a thick silica glass layer 22, such as 400 nm thick, is deposited over the structure.

The sample can then be measured with a far-field measuring device. The measured optical image shows detection of a significant amount of emitted light from the output antenna. This implies good coupling and propagation of surface plasmon polariton (SPP) guided modes in the plasmonic slot waveguide shown in FIG. 3C.

FIG. 4A is an SEM image of an exemplary plasmonic slot waveguide nanocircuit on an optical facet. FIG. 4B is an enlarged SEM image of the waveguide of FIG. 4A. FIG. 4C is an SEM image of another exemplary plasmonic slot waveguide on an optical facet. FIG. 4D is an enlarged SEM image of the waveguide of FIG. 4C. 4A-4D show waveguide nanocircuits 10A on facets 8, which can be formed on conventional polarization-maintaining (PM) optical fibers 4 or on PM photonic crystal fibers, by way of example. The 90° bend is used to change the waveguide mode polarization of the radiating antenna, thus enabling cross-polarized far-field imaging with good signal-to-noise ratio of the desired output signal (forward propagating incident light inhibit). PCFs are used to ensure plasmonic waveguide/antenna alignment during nanofabrication and optical measurements. Far-field measurements have shown that light from the core mode can couple efficiently with the plasmonic waveguide mode, and that the in-plane plasmonic mode can propagate and radiate in the radiating antenna with orthogonal output polarizations. For an input core polarization orthogonal to the antenna direction, little or no light is emitted from the radiating antenna, indicating coupling of the plasmonic mode with the desired polarization state. Typical core diameters for conventional single-mode fibers and photonic crystal fibers are about 4-6 μm, and the size of Yagi-Uda antennas is about 1 μm. To efficiently utilize the entire core mode region, the present invention can include multiple complex structures with multiple input antennas. Sophisticated nanostructures with multiple inputs can greatly improve the overall coupling efficiency to plasmonic nanocircuits.

5A-5D show exemplary NIR optical camera images and associated responses of incident light in a plasmonic slot waveguide nanocircuit at wavelengths 1550 nm and 1630 nm. FIG. 5A is an overlay of optical and SEM images of waveguide nanocircuits. FIG. 5B is an SEM image of the waveguide and output at a wavelength of 1550 nm. FIG. 5C is an SEM image of the waveguide and output at a wavelength of 1630 nm. FIG. 5D is a chart showing exemplary coupling efficiencies for a single waveguide in the wavelength range of 1500-1630 nm. In FIG. 5A, the exemplary single waveguide 10A couples light from input antenna 26 at input port 32 and radiates light from output antenna 28 at output port 34 in the outer cladding of the core. In FIG. 5B, at 1550 nm, the output light is brighter than the input light. In FIG. 5C, at 1630 nm, the input light is brighter than the output light. Near-infrared (NIR) images of the facets are recorded in the range 1500-1630 nm with a step size of 5 nm. These images of the coupled output antenna are then normalized to images of a blank PS fiber of similar length with the same input laser power. This normalized data shows the coupling efficiency of a single waveguide in the wavelength range of 1500-1630 nm, as shown in FIG. 5D. The results show that the total efficiency (including input/output coupling, bend loss, and propagation loss) of the single exemplified waveguide is measured to be about 0.2% in the wavelength range of 1500-1630 nm. ing.

6A-6I illustrate exemplary plasmonic multi-channel waveguide structures fabricated on photonic crystal fiber and PM-PCF fiber. FIG. 6A is an SEM image of a multi-channel waveguide nanocircuit on a fiber optic facet 8 of a photonic crystal fiber. FIG. 6B is a measured far-field optical image showing four output signals. FIG. 6C is an image near the core and output region of the optical fiber. This example shows a nanocircuit 10A with four identical input antennas 26 and four separate waveguides 30 with different lengths (15, 12, 9, 6 μm). The measured optical images show that the optical fiber core modes are coupled and distributed into four separate plasmonic waveguides, with the shortest waveguide having the highest output intensity, as shown in FIGS. 6B and 6C. , showing a gradual decrease in intensity with increasing waveguide length. The measured plasmonic waveguide loss is about 0.45 dB/μm at a wavelength of 1550 nm (by transmission spectrum measurements at different waveguide lengths). Yagi-Uda antennas can maximize coupling efficiency by designing parameters (length, width, gap size, etc.). Full-wave electromagnetic 3D simulations show that a coupling efficiency of about 6% (for non-optimized antennas) can be achieved from a 6 μm core mode to a single plasmonic waveguide with a slot width of 300 nm. For example, integrating 4 or 5 input antennas can yield a coupling efficiency of about 30%, and optimizing the antenna and core geometry can yield a coupling efficiency of over 50%. An efficient plasmonic system on the fiber tip is obtained.

FIG. 6G is an SEM image of a multi-channel waveguide nanocircuit similar to that of FIG. 6A formed on a polarization-maintaining photonic crystal fiber (PM-PCF). FIG. 6H is an enlarged SEM image of the multi-channel waveguide nanocircuit of FIG. 6G. FIG. 6I is a magnified SEM image of the multichannel waveguide nanocircuit of FIG. 6H showing the input antenna near the core of the optical fiber. Additional embodiments demonstrate the ability to form on multiple optical fibers.

Figures 7A-7E show exemplary plasmonic directional coupler nanocircuits with multiple output channels fabricated on PM optical fibers. FIG. 7A is an SEM image of an optical fiber facet before fabrication of an integrated directional coupler nanocircuit. FIG. 7B is a magnified view of an optical fiber facet after an exemplary plasmonic directional coupler has been fabricated. FIG. 7C is a further enlarged view of the plasmonic directional coupler of FIG. 7B. FIG. 7D is a measured far-field optical image showing two outputs at 1550 nm. FIG. 7E is a measured far-field optical image showing two outputs at 1630 nm. The teachings herein can be used to create a plasmonic directional coupler nanocircuit 10C. As an example, a plasmonic directional coupler can be fabricated on facet 8 of panda-shaped PM optical fiber 4 shown in the SEM images of FIGS. 7A and 7B. The present invention uses such plasmonic directional couplers to provide optical switching properties. The plasmonic directional coupler includes two adjacent waveguides 30A and 30B, with one single waveguide extending parallel to the other along the horizontal portion of each waveguide. (In Figures 7A and 7B, the structure can be made according to the slow/fast axis of the PM fiber for cross-polarized far-field detection by etching a circular ring to help identify the "panda" structure in the cladding. .) In this example, the two slot waveguides 30A and 30B have a width of 300 nm, a distance between the waveguides of 80 nm, and a coupling length of 3 μm. The Yagi-Uda antennas at the input antenna 26A and the output antenna 28A are 22 μm long (horizontal portion) and the portion of the vertical slot waveguide connected to the output antenna is 6 μm, consistent with the single slot waveguide 30A. The other slot waveguide 30B, which runs parallel to the wavelength from the input, has a horizontal length of 10 μm over which evanescent field coupling is observed. Both ends of the additional slot waveguide can be aligned with the output antenna 28B after a ⁹⁰⁰ bend and vertical waveguide. Power in one waveguide can be evanescently coupled back and forth into the other waveguide. For example, the thickness of the thin metal film separating the two parallel-extending waveguides can be in the range of 50-100 nm. Depending on the coupling length and operating wavelength (affecting the coupling coefficient of the two waveguides), the optical power can be switched between different waveguide outputs or evenly distributed between the two waveguides. Light is coupled through the core and can be emitted from output port O1 or output port O2 depending on the operating wavelength. The polarization state of the incident light matches the orientation of the input antenna, effectively assisting the coupling of SPP modes in the slot waveguides, as described above.

Simulations show that, in at least one embodiment, a 550% emission ratio from waveguide 30A to waveguide 30B can be achieved. The results show that light can be coupled into the plasmonic directional coupler and emitted equally from output ports O1 and O2 at a wavelength of 1550 nm, as shown in FIG. 7D. At a wavelength of 1630 nm, more light is emitted through the output port O2, as shown in FIG. 7E, exhibiting initial directional coupling characteristics and resulting switching characteristics. Further optimization can be done by varying the separation and bond lengths.

FIG. 7F is an SEM image of a panda-type (PS) fiber optic facet with another exemplary integrated directional coupler nanocircuit. FIG. 7G is a superimposed image of far-field measurements at a wavelength of 1630 nm for the exemplary plasmonic directional coupler of FIG. 7F. FIG. 7H is a far-field image of the plasmonic directional coupler of FIG. 7F using a supercontinuum (SC) source laser without optical filters. FIG. 7I is a measured far-field optical image at a wavelength of 1480 nm detected with cross-polarization to the incident light. FIG. 7J is a measured far-field optical image at a wavelength of 1550 nm detected with cross-polarization to the incident light. FIG. 7K is a measured far-field optical image at a wavelength of 1650 nm detected with cross-polarization to the incident light. A CW supercontinuum (SC) laser and bandpass filters are utilized for far-field measurements of nanocircuits. FIG. 7G is a superimposed image of the far-field optical measurement image and the SEM image, clearly showing the coupling of the outputs. FIG. 7H shows clear coupling at the output antenna with the SC light source when no filters are used and light is conducted to all antennas on the waveguide. FIG. 7I is a far-field measurement using a bandpass filter with a wavelength of 1480 nm and a bandwidth of ±10 nm. This measurement shows a higher intensity at output port O1 (O1=cross output, intensity lcross) compared to output port O2 (O2=bar output, intensity Ibar). FIG. 7J shows that the intensities of the two output ports O1, O2 at 1550 nm are approximately equal. FIG. 7K shows higher intensity at output port O2 at 1650 nm. FIG. 7J thus shows the power coupling between FIGS. 7I and 7K.

Embodiments shown in other figures represent prophetic embodiments. Figures 8A-8F show other nanocircuits in the form of polarization splitter nanocircuits. FIG. 8A is an SEM image of an exemplary polarization splitter. FIG. 8B is an enlarged SEM image of the input antenna of the polarization splitter of FIG. 8A. FIG. 8C is a measured far-field optical mirror image of the polarization splitter of FIG. 8A, showing horizontal incident polarization transmitted through a waveguide with a horizontally aligned input antenna. FIG. 8D is a measured far-field optical mirror image of the polarization splitter of FIG. 8A, showing vertically incident polarization transmitted through a waveguide with a vertically aligned input antenna. FIG. 8E is a chart showing the transmission strength as a function of each horizontal or vertical arrangement with horizontal and vertical polarization inputs for each waveguide shown in the polarization splitter of FIG. 8A. FIG. 8F is a chart showing the transmitted power as a function of each horizontal or vertical alignment with a rotationally polarized input that is not in the horizontal or vertical plane for each waveguide shown in the polarization splitter of FIG. 8A.

The polarization splitter 10D enables the ability to switch the output signal of the nanocircuit on the fiber in the core mode polarization state. The embodiment of FIG. 8A and the embodiment magnified in FIG. 8B allow the input antennas 26A-26D (generally 26) to be axially aligned with the fiber core. The input antennas 26 are arranged horizontally and vertically in the SEM image, ie, generally at right angles. One set of left and right input antennas 26A and 26B in the image of FIG. 8B are aligned vertically and correspond to antennas 28A and 28B that provide outputs after bending of waveguides W1 and W2. Another set of input antennas 26C and 26D at the top and bottom of the image of FIG. 8B are arranged horizontally and correspond to antennas 28C and 28D that provide outputs after bending of waveguides W3 and W4. For optical measurements, an additional optical component called a half-wave plate can be added immediately after the linear polarizer at the input end. The half-wave plate can be rotated in any direction to change the polarization state of the incident light entering the fiber. The use of this half-wave plate results in a 2θ change in polarization when rotated through an angle θ, but has nearly zero effect on the coupling/alignment of the optical path. For example, as shown in FIG. 8C, the horizontal polarization state of the incoming signal in the fiber excites the input antennas 26C, 26D aligned to their respective polarizations, thus illuminating waveguides W3 and W4. Transmission is observed. Similarly, if the polarization is switched to a vertical polarization state, the incident signal in the fiber will excite the input antennas 26A, 26B matched to their respective polarizations, thus lighting waveguides W1 and W2. , the transmission is observed. If the light is incident at any other angle, we get the transmission as their unique component in each direction. Ideally, one should observe that each of the four output antennas radiates the signal evenly when the incident polarization state is 45° to the horizontal. The example shown in FIG. 8F is primarily useful for demonstrating the concept rather than the exact degree, as test data and the preparation of this example focus experimentally at different angles.

9A-9D are an example set of diagrams for a miniature resonant waveguide network (RGWN) nanocircuit 10E for an optical fiber tip. FIG. 9A shows an SEM image of an exemplary RGWN nanocircuit fabricated on a planar substrate. FIG. 9B shows a measured optical image of an RGWN structure with a resonance size of 7.5 μm, showing output port O1 high and output port O2 low at a wavelength of 1570 nm. FIG. 9C is a measured optical image of the RGWN structure of FIG. 9B showing output port O1 low and output port O2 high at a wavelength of 1550 nm. A comparison of Figures 9B and 9C shows the switching characteristics of the RGWN at different wavelengths. FIG. 9D shows SEM images of RGWNs fabricated with different sizes to demonstrate the potential of fiber optic facets in nanocircuits.

Figures 10A-10F show schematics of microminiaturized RGWN nanocircuits and various graphs showing the results. FIG. 10A is an SEM image of an exemplary embodiment of an ultra-compact RGWN nanocircuit 10E' with a cavity size of 300 nm. FIG. 10B is a measured optical image of the RGWN of FIG. 10A. FIG. 10B shows efficient coupling to three output ports. FIG. 10C is an SEM image of another exemplary embodiment of RGWN 10E″ with a cavity size of 7.5 μm. FIG. 10D is a chart showing exemplary measured and simulated spectra for port O1 of the RGWN of FIG. 10C. FIG. 10E is a chart showing exemplary measured and simulated spectra for port O2 of the RGWN of FIG. 10C. FIG. 10F is a chart showing exemplary measured and simulated spectra for port O4 of the RGWN of FIG. 10C.

In at least one embodiment, the plasmonic RGWN nanocircuit 10E (shown in FIG. 9A), 10E′, 10E″ (generally 10E) is an optical nanocircuit in which coherent interference of plasmonic waves creates multiple resonances within the network. It can be used on fiber. To integrate the RGWN onto an optical fiber, for example, a Yagi-Uda antenna can be used to optically couple the optical core mode into the RGWN. A high numerical aperture (“NA”) objective lens can be used to focus the laser to a spot of about 1 μm to excite the input antenna. Measured far-field patterns of the RGWN at wavelengths 1570 nm and 1550 nm are shown in FIG. 10B. This figure shows that the output signal is highly wavelength dependent. The "off/on" or "high/low" output states can be varied with different wavelengths, thus indicating wavelength selective devices and wavelength demultiplexing properties due to resonant interference. By using this RGWN, it is possible to develop a very small circuit with a wavelength selection function. As shown in FIGS. 10C and 10A, it is believed that RGWNs with resonant sizes from about 7.5 μm to about 300 nm can be routinely fabricated with good transmission. It is believed that this plasmonic RGWN can reach at least sub-100-nanometer scale sizes while maintaining coherent wave interference. The emission spectrum of the 7.5 μm resonant size RGWN of FIG. 10C was measured and the results for ports O1, O2 and O4 are shown in FIGS. 10D-10F. The measured spectral beat indicates the nature of resonance due to the interference of multiple propagating waves. The numerical simulation results for line 36 closely match the spectral response and amplitude of the experimental results for line 38, indicating that RGWNs can be used to develop nanoscale resonant devices.

With differences in network sizes and grids, the present invention can provide resonant waveguide networks that can be used for permutations of Boolean on/off values and distribution of optical signals at the nanoscale. Plasmonic RGWNs can be used for on-fiber compact optical logic or wavelength multiplexing/demultiplexing devices at telecommunications wavelengths, and can be used in different on/off combinations for the development of fiber-coupled nanocircuits. Route wavelengths to different transmission ports.

The present invention can further improve plasmonic structures by combining the strong electrical tunability and ENZ nonlinearity of field-effect conductive oxide materials with the concept of resonant waveguide networks and directional couplers. . The result is an electrically gateable, ultrafast, nonlinear optically tunable plasmonic network with over 100 on/off Boolean states for ultrafast (>100 GHz) switching, coupling, and multi-channel logic components. can function as

Figures 11A-11D show an example of a tunable RGWN nanocircuit 10E''' reconfigurable for active signal processing and associated schematics and optical images. FIG. 11A is a schematic diagram of an example of a tunable RGWN nanocircuit. FIG. 11B is a schematic diagram of a corresponding transparent conducting oxide (TCO) waveguide. FIG. 11C shows the simulated response with applied bias. FIG. 11D is the simulated response with no bias applied, demonstrating ultra-fast switching capability. At least one embodiment includes selective integration of ENZ materials into the sub-wavelength dimension antenna-coupled plasmonic slot waveguide network 10E''' shown in FIGS. 11A and 11B. To actively control the resonant behavior of in-fiber plasmonic RGWNs, the present invention uses field-effect tuning of ENZ materials such as conductive oxides or nitrides in MOS-type structures, as shown in FIG. 11B. Is possible. The exemplary MOS device includes a metal layer 16 that can be used to form nanocircuitry portions, a dielectric insulator layer 42 over the metal layer 16, and a TCO layer. As used herein, "TCO" materials include ITO, AZO, or TiN and similar materials with transparency and electronic conductivity properties. Dielectric insulators generally have high dielectric values, such as aluminum _oxide ( _Al2O3 ), hafnium dioxide ( _HfO2 ), aluminum doped zinc oxide (AZO), or other materials with suitable dielectric insulating properties. are mentioned. Depositing a metal layer 16 on the facets 8 of the optical fiber 4 and milling to form slots 20, nanocouplers (such as antennas), and other structures for nanocircuits, as described in FIG. 3A. can be done. Dielectric insulator layer 42 may be deposited on metal layer 16 by atomic layer deposition (ALD) or sputtering, for example, after a focused ion beam (FIB) milling/electron beam lithography step on the metal layer. A TCO layer 44 may be deposited over the dielectric insulator layer 42 . The metal layer, dielectric insulator layer, and TCO layer can be bonded by wire bonding techniques or physical contact with a specially designed fiber holder. This coupling allows efficient control of optical confinement based on the stored electron distribution and the tunable dielectric constant for controllable phase and amplitude, thus controlling the resonant properties of the network. becomes possible. In particular, when the signal wavelength approaches the ENZ resonance of the voltage-tuned conductive oxide accumulation layer, the effective refractive index of the propagating mode increases, thus leading to strong modulation of the resonance signal.

Numerical simulation results for electrical modulation are shown in FIGS. 11C and 11D. The signals of the two output ports in the "on/off" state at the top of the image can be alternately switched by applying a gate voltage of, for example, 3V. The field effect tuning capability of TCO ENZ influences the switching characteristics of plasmonic directional couplers. By reducing the size of the TCO field-effect structure (eg, 2-3 μm) with the small gate capacitance of the RGWN or directional coupler, the operating speed of the modulation can be increased from tens of GHz to very low energy consumption (less than 1 fJ/bit). It can exceed hundreds of GHz.

The unusually large ENZ nonlinearities of TCO materials can be exploited to dynamically control complex lightwaves and functions in plasmonic nanocircuits. The anomalously large ENZ nonlinearities of TCO materials include the anomalously high nonlinear refractive index (n2) and nonlinear absorption coefficient (β2) of AZO ENZ thin films near the ENZ wavelength. The measured coefficient n2(eff) of about 10 ⁻⁸ mm ² /W and coefficient β2(eff) of about −10 ⁻⁴ cm/W were obtained using a Z-scan nonlinear measurement technique using an ultrafast femtosecond laser with a wavelength of 1550 nm. obtained by The measured nonlinearity of ENZ thin films is strong (2-3 orders of magnitude higher than highly nonlinear chalcogenide glasses) and can be further tuned by ALD parameters during deposition of AZO materials.

Figures 12A-12D show an example of a nanocircuit as a tunable directional coupler and an associated schematic. FIG. 12A is a schematic diagram of an exemplary tunable ENZ/plasmonic directional coupler nanocircuit 10C for nonlinear optical switching. FIG. 12B is a schematic diagram of an exemplary corresponding ENZ waveguide of the directional coupler of FIG. 12A. FIG. 12C is a simulated field profile of a low pump power ENZ/plasmonic directional coupler. FIG. 12D shows a simulated field profile of an ENZ/plasmonic directional coupler with high pump power. Combining the nonlinearity of ENZ with plasmonic nanostructures enables ultrafast optical control of optical fiber nanocircuits. The ultrafast optically tunable properties of plasmonic slot waveguides, such as FIG. 6A, and plasmonic directional couplers, such as FIG. 7C, can be achieved by using a TCO layer on top of metal layer 16 as shown in FIG. 12B. 44 can be demonstrated. For example, a 20-30 nm thick TCO layer 44 exhibiting an ENZ wavelength at the femtosecond laser operating wavelength (eg, 1550 nm) can be deposited on the metal layer 16 of the slot plasmonic waveguide by ALD/sputtering techniques. The silicon oxide layer 24 described in FIG. 3A can be deposited over the TCO layer 44 . Due to the strong optical confinement of plasmonic waveguides and the high optical nonlinearity of ENZ, the phase and amplitude of propagating plasmonic waves can be altered by ultrafast femtosecond pulses. Simulations of optical propagation changes in AZO ENZ plasmonic slot waveguides using nonlinearities measured with Z-scan techniques are presented. A large nonlinear-optically-induced refractive index change is obtained near the ENZ wavelength, increasing the effective index of the mode from 1.515+0.308i (low power) to 1.569+0.136i (high power) at the ENZ wavelength. . This change can reduce the propagation loss of the mode from 10.33 dB/μm (low power) to 4.57 dB/μm (high power), changing the field confinement as shown in FIGS. 12C and 12D. ENZ enhancement of nonlinear effects can be used in plasmonic couplers as shown in FIG. 7A and RGWNs as shown in FIG. High-dispersion optical directional couplers provide a platform for the nonlinear response of ENZ materials to significantly affect the power dependence of the system. Strong nonlinear switching effects can occur when the output radiation from the two output ports strongly depends on the incident laser power.

A combination of electrical and optical coherent control of the spatial and temporal variation of propagating plasmon modes in RGWNs emits femtosecond laser pulses to excite multiple eigenmodes in the coupler, while further controlling eigenstate dispersion. can be studied by providing electrical gating to In general, the present invention is capable of integrating active conductive oxide materials with plasmonic structures to provide efficient novel nanodevice applications and next-generation ultra-compact, fast-integrated nanocircuits with ultra-low power consumption. and enable active optical components.

The efficient coupling and functioning of fiber optic nanocircuits enables a variety of high-level applications based on ultra-high density plasmonic nanocircuits. For example, non-limiting examples include fiber optic input/output signal processing, quantum emission enhancement of in-fiber quantum sources, ultra-sensitive optical/molecular sensing, and the like.

13A-13G are schematic diagrams of exemplary structures of fiber optic ENZ nanocircuits for integrated optical communications. To demonstrate the concept of using fiber optic tipped nanocircuits as microintegrated circuits for nanoscale signal processing and manipulation, the following three embodiments can be presented.

FIG. 13A is an exemplary tunable fiber optic ENZ nanocircuit device 2′ having an optical fiber with a single mode core 6, a nanocircuit 10 on the tip of the optical fiber, and an output multicore optical fiber 12 with an output port 14. 1 is a schematic diagram showing a preferred embodiment; FIG. This embodiment provides electronic or nonlinear optical dynamic control by a tunable nanocircuit 10 on the tip of an optical fiber whose input is from a single-mode core 6 for input to the tunable nanocircuit. have As shown in FIGS. 13D and 13E, multicore optical fiber 12 is closely coupled with nanocircuit 10 to receive inputs from the nanocircuit for multiple outputs 14 from the multicore optical fiber. As shown in the structure in FIG. 13F and the enlarged view in FIG. 13G, depending on the incident vertical/horizontal polarization, specific output ports of the structure can be selectively excited, thereby providing coherent signal and output selection. Other means of manipulating the can be provided.

13B is a schematic diagram illustrating another exemplary embodiment of a tunable optical fiber ENZ nanocircuit device 2'' having a single mode core 6. FIG. This embodiment provides electronic or nonlinear optical dynamic control by a tunable nanocircuit 10 on the tip of an optical fiber whose input is from a single-mode core 6 for input to the tunable nanocircuit. have The multicore optical fiber 10 is intimately coupled with the nanocircuit to receive input from the nanocircuit for multiple outputs 14 having one or more different characteristics than the multicore optical fiber 12 . Such embodiments are envisioned to be useful for optical switching, wavelength demultiplexing, resonant interference, or routing/Boolean logic, and other applications.

FIG. 13C is a schematic diagram showing an exemplary tunable fiber optic ENZ nanocircuit device 2''' having a multi-core fiber 6' for providing multiple inputs to the nanocircuit. Multiple input lights through multicore fiber 6' are coupled into nanocircuit 10' (such as an RGWN or a directional coupler) and coherently interfere via linear or nonlinear interactions, resulting in dispersion and phase/ It is possible to provide a high degree of control over amplitude modulation. The nanocircuit can be configured to receive multiple incident lights from the core 6'. A time-resolved pump-probe device allows nonlinear dynamics to be probed through a multicore fiber. For the electrical control of fiber nanocircuits, high-speed electronics and detectors can be used to monitor output signals at operating speeds as high as tens of GHz. In this embodiment, the input is from a multicore fiber, with electronic or nonlinear optical dynamic control by a tunable nanocircuit at the tip of the optical fiber. The output multicore optical fiber 12 is closely coupled with the nanocircuit to receive input from the nanocircuit for multiple outputs of different nature. Light is emitted from multiple output ports of the nanocircuit and is coupled directly to an output multicore optical fiber 12 for light collection by, for example, a spectrometer or detector. To achieve such nanocircuit functionality, ENZ materials can be used to achieve electrical and nonlinear optical tunability. The output signals of the multiple output ports can be controlled by applying a bias or by emitting ultrafast femtosecond pulses, as referred to herein. A similar detection scheme can be used to collect light through an output multicore optical fiber, as shown in FIGS. 13A and 13B. Devices 2 with polarization dependent coupling can also be used as a means of controlling nanocircuits.

It is known that the emission and nonlinear optical processes of molecules/materials strongly depend on the electromagnetic field strength and can be greatly enhanced by plasmonic structures due to the high degree of confinement of plasmonic modes. Recent studies have shown that the use of on-chip plasmonic slot waveguides enhances molecular Raman emission. This emission enhancement is due to an enhancement of the electric field and Purcell factor, an increase in the amount of light and matter interaction, and an increase in Raman signal collection efficiency. Also, in recent years, some studies have been reported on the plasmonic Purcell effect and the coupling of quantum emitters and ENZ materials. The present invention goes beyond current understanding to combine the field confinement of ENZ nanolayers and the long interaction length of plasmonic slot waveguides on optical fiber tip nanocircuits to enhance the radiation enhancement capabilities of ENZ/plasmonic materials. It is used further.

14A-14C illustrate an example of a fiber optic plasmonic waveguide sensor nanocircuit 10F for enhancing Raman and optical sensing. Such nanocircuits support the integration of the plasmonic waveguides herein by better interaction with molecules and can receive input from one or more of the nanocircuits described above. FIG. 14A is a schematic diagram of a fiber optic plasmonic waveguide sensor. FIG. 14B is an enlarged view of the nanostructures of FIG. 14A. FIG. 14C shows an example of a sensor nanocircuit 10F fabricated in an optical fiber with long interaction length. The sensor can be waveguided by depositing and milling a metal layer 16 as described above. However, in this nanocircuit, the waveguide terminates as a "dead end" before exiting the metal layer, rather than a through path like the other waveguides described. Such ends 46 reflect energy within waveguide 30 . The present invention utilizes enhanced spontaneous/Raman emission from the emitter in the ENZ region using a TiN/TCO ENZ coated plasmonic slot waveguide on the tip of an optical fiber, shown in FIGS. 14A and 14B. It is possible. ENZ thin films can be deposited on plasmonic slot waveguides on the facets of optical fibers using ALD techniques, and the molecules/emitters can be stacked on the optical fiber facets. Light 50 can be coupled through core 6 to excite plasmonic modes in plasmonic slot waveguide 30 . Propagating plasmonic light can interact with the molecules/emitters in slot 20 and emitted light 52 can couple back to the core. The Raman signal/spectrum can be collected in reflection of the fiber using a beamsplitter. To ensure sufficient light-matter interaction length while balancing propagation losses, novel structures with moderate lengths, such as spiral waveguides as shown in FIG. , can be fabricated on the fiber core facet to terminate at the end 46 of the waveguide for stronger optical reflection. Emission measurements of nanocircuits with and without an ENZ layer are compared to reveal enhancement of emission by ENZ.

Emission enhancement arises from a high local density of states near the ENZ surface and is highly dependent on the dipole orientation of the emitter, which is efficiently coupled to the ENZ resonance. Similar coupling schemes in plasmonic slot waveguides can be used for enhanced photoluminescence and simulated/spontaneous emission of emitters (quantum dots, upconversion nanocrystals, laser materials, etc.) using ENZ plasmonic nanocircuits. can. Quantum emission enhancement in optical fiber nanocircuits may lead to advanced applications of on-fiber quantum sources and in-fiber Raman sensing.

Other and further embodiments utilizing one or more aspects of the above-described invention can be devised without departing from the disclosed invention as defined in the claims. For example, other embodiments include other shapes and types of optical fibers, other ENZ materials for forming films on or within optical fibers, other MOS structures and materials, other thicknesses and frequencies, And other variations than those specifically disclosed above may be included within the scope of the claims.

The invention has been described in connection with preferred and other embodiments, and not all embodiments of the invention have been described. Obvious modifications and alterations to the described embodiments are available to those skilled in the art. The disclosed and undisclosed embodiments are not intended to limit or limit the scope or applicability of any invention devised by applicant; rather, pursuant to patent law, applicant: It is intended to fully protect all such modifications and improvements that come within the scope of the following claims or the equivalents.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is based on U.S. Provisional Patent Application Serial No. 63/032,050, entitled "Tunable Nanophotonic Waveguide Systems and Methods," filed May 29, 2020. claimed, the contents of which are incorporated herein by reference.

1 is a schematic diagram of one embodiment of a nanocircuit system according to the present invention; FIG. 1 is a schematic illustration of a fabrication process for forming an integrated nanocircuit on a facet (hereinafter also referred to as "tip") of an optical fiber; FIG. 1 is a schematic diagram of an exemplary fiber optic nanocircuit having a slot plasmonic waveguide with an antenna; FIG. 1 is a schematic diagram of an exemplary antenna for coupling an optical fiber mode to a plasmonic slot waveguide mode; FIG. 3B is a schematic diagram of the vertical profile of the plasmonic slot waveguide mode shown in FIG. 3A showing the electric field component of the light in the slot; FIG. SEM image of an exemplary plasmonic slot waveguide nanocircuit on an optical facet. 4B is an enlarged SEM image of the waveguide of FIG. 4A; FIG. 4B is an SEM image of another exemplary plasmonic slot waveguide on an optical facet; FIG. 4D is an enlarged SEM image of the waveguide of FIG. 4C; FIG. 2 is a superimposed optical and SEM image of a waveguide nanocircuit; SEM image of the waveguide and the output at a wavelength of 1550 nm. SEM images of the waveguide and the output at a wavelength of 1630 nm. 4 is a chart showing exemplary coupling efficiencies for a single waveguide in the wavelength range of 1500-1630 nm; SEM images of multi-channel waveguide nanocircuits on optical fibers. 4 is a measured far-field optical image showing four output signals; FIG. 4 is a close-up of a measured far-field optical image near the core and output region of an optical fiber; FIG. 6B is a magnified SEM image of the multi-channel waveguide nanocircuit of FIG. 6A. FIG. 6C is an enlarged SEM image of the multi-channel waveguide nanocircuit of FIG. 6D showing the output antenna ports. 6E is a magnified SEM image of the multi-channel waveguide nanocircuit of FIG. 6E showing the input antenna near the core of the optical fiber. 6B is an SEM image of a multi-channel waveguide nanocircuit similar to that of FIG. 6A formed on a polarization-maintaining photonic crystal fiber (PM-PCF). FIG. 6G is a magnified SEM image of the multi-channel waveguide nanocircuit of FIG. 6G. 6H is a magnified SEM image of the multi-channel waveguide nanocircuit of FIG. 6H showing the input antenna near the core of the optical fiber. SEM images of optical fiber facets before the fabrication of integrated directional coupler nanocircuits. FIG. 4B is a close-up view of the fiber optic facet after the exemplary plasmonic directional coupler has been fabricated. Figure 7C is a further enlarged view of the plasmonic directional coupler of Figure 7B; Measured far-field optical images showing two outputs at 1550 nm. Measured far-field optical images showing two outputs at 1630 nm. FIG. 11 is an SEM image of a panda-type (PS) fiber optic facet with another exemplary integrated directional coupler nanocircuit; FIG. FIG. 7F is a superimposed image of far-field measurements at a wavelength of 1630 nm for the exemplary plasmonic directional coupler of FIG. 7F. 7F is a far-field image of the plasmonic directional coupler of FIG. 7F using a supercontinuum (SC) source laser without optical filters. Far-field optical image measured at a wavelength of 1480 nm detected with cross-polarization to the incident light. Far-field optical image measured at a wavelength of 1550 nm detected with cross-polarization to the incident light. Far-field optical images measured at a wavelength of 1650 nm detected with cross-polarization to the incident light. FIG. 4 is an SEM image of an exemplary polarization splitter nanocircuit; FIG. 8B is an enlarged SEM image of the input antenna of the polarization splitter of FIG. 8A; 8B is a measured far-field optical mirror image of the polarization splitter of FIG. 8A showing horizontal incident polarization transmitted through a waveguide with a horizontally aligned input antenna; FIG. 8B is a measured far-field optical mirror image of the polarization splitter of FIG. 8A showing vertical incident polarization transmitted through a waveguide with a vertically aligned input antenna; FIG. 8B is a chart showing the transmission strength as a function of horizontal or vertical alignment, respectively, with horizontal and vertical polarization inputs for each waveguide shown in the polarization splitter of FIG. 8A; 8B is a chart showing the transmission strength as a function of respective horizontal or vertical alignments with rotationally polarized input not in the horizontal or vertical plane for each waveguide shown in the polarization splitter of FIG. 8A; FIG. 10 is an SEM image of an exemplary resonant waveguide network (RGWN) nanocircuit fabricated on a planar substrate; 4 is a measured optical image of an RGWN with a resonance size of 7.5 μm, showing the output at a wavelength of 1570 nm. FIG. 8C is a measured optical image of the output of the RGWN of FIG. 8B at a wavelength of 1550 nm. Fig. 4 is an SEM image of fabricated RGWNs of different sizes; SEM image of an exemplary embodiment of an ultra-small RGWN nanocircuit with a cavity size of 300 nm. 10B is a measurement optical image of the RGWN of FIG. 10A; FIG. 4B is an SEM image of another exemplary embodiment of an RGWN with a cavity size of 7.5 μm; FIG. 10D is a chart showing exemplary measured and simulated spectra for Port 1 of the RGWN of FIG. 10C; 10D is a chart showing exemplary measured and simulated spectra for port 2 of the RGWN of FIG. 10C; 10D is a chart showing exemplary measured and simulated spectra for port 4 of the RGWN of FIG. 10C; 1 is a schematic diagram of an example of a tunable RGWN nanocircuit; FIG. Fig. 2 is a schematic diagram of a corresponding transparent conducting oxide (TCO) waveguide; FIG. 11 shows a simulated response when bias is applied; Fig. 10 shows a simulation response with no bias applied, demonstrating ultra-fast switching capability; FIG. 2 is a schematic diagram of an exemplary tunable ENZ/plasmonic directional coupler nanocircuit for nonlinear optical switching; 11B is a schematic diagram of an exemplary corresponding TCO waveguide of the directional coupler of FIG. 11A; FIG. Fig. 3 shows a simulated field profile of a low pump power ENZ/plasmonic directional coupler; Fig. 3 shows a simulated field profile of an ENZ/plasmonic directional coupler with high pump power; 1A-1C are schematic diagrams illustrating exemplary embodiments of a tunable optical fiber ENZ nanocircuit having an optical fiber with a single-mode core, a nanocircuit on the tip of the optical fiber, and a multi-core optical fiber. FIG. 10 is a schematic diagram illustrating another exemplary embodiment of a tunable optical fiber ENZ nanocircuit with a single mode core; FIG. 2 is a schematic diagram showing an exemplary tunable fiber optic ENZ nanocircuit with multi-core fibers for providing multiple inputs to the nanocircuit; 1 is a schematic diagram of an exemplary multi-core optical fiber; FIG. 13D is an enlarged schematic diagram of the multi-core optical fiber of FIG. 13D; FIG. Exemplary nanocircuits that can be intimately coupled with the multicore optical fiber of FIG. 13D 1 is a schematic diagram showing the . 13F is a partially enlarged schematic diagram of the nanocircuit of FIG. 13F; FIG. 1 is a schematic diagram of a fiber optic plasmonic waveguide sensor; FIG. 14B is an enlarged view of the nanostructures of FIG. 14A. FIG. FIG. 3 shows an example of a structure fabricated in an optical fiber with long interaction length;

Claims (20)

a first optical fiber faceted;
nanocircuits integrally formed on the facets;
The nanocircuit is
a nanocoupler configured to directly couple optical energy from the first optical fiber with plasmonic energy in the nanocircuit;
at least one waveguide formed in said nanocircuit, coupled to said nanocoupler and configured to conduct plasmonic energy in said nanocircuit. 2. The device of claim 1, wherein the first optical fiber is a multi-core fiber configured to provide multiple inputs to the nanocircuit. 2. The device of Claim 1, further comprising a second optical fiber coupled to said nanocircuit and configured to receive power from said nanocircuit and emit optical energy. 4. The device of claim 3, wherein said second optical fiber is a multi-core fiber having multiple output ports. 5. The device of claim 4, wherein the first optical fiber is a multicore fiber configured to provide multiple inputs to the nanocircuit. The waveguide is formed in a metal layer and further comprises a dielectric layer deposited on the metal layer and a transparent conductive oxide layer deposited on the dielectric layer, wherein an applied bias causes the nanocircuit to 2. The device of claim 1, wherein the resonance of said dielectric layer and said transparent conducting oxide layer is changed to modulate phase and amplitude. 2. The device of claim 1, wherein the nanocircuit comprises an output, the amount of energy from the output being dependent on the electrical bias applied to the nanocircuit. 2. The device of claim 1, wherein the nanocircuit comprises an output, the amount of energy from the output being dependent on the frequency of light energy to the nanocircuit. The nanocircuit comprises a plurality of waveguides, each waveguide of the plurality of waveguides having an input nanocoupler and an output nanocoupler formed therein, the output nanocoupler emitting energy from the waveguides. 11. The device of claim 1, configured to. 2. The device of claim 1, wherein at least one waveguide of said plurality of waveguides has a different length than at least one other waveguide of said plurality of waveguides. The nanocircuit comprises a directional coupler, the directional coupler comprising:
a first waveguide having an input nanocoupler and an output nanocoupler;
a second waveguide having an input nanocoupler and an output nanocoupler;
The second waveguide has a length aligned closely parallel to the length of the first waveguide configured to couple an evanescent field between the first and second waveguides. have
A device according to claim 1 . A change in the frequency of optical energy provided to the input nanocoupler of the first waveguide relative to the output nanocoupler of the second waveguide is the output nanocoupler of the first waveguide. 12. The device of claim 11, which alters the emission of light energy of the . The nanocircuit comprises a polarization splitter, the polarization splitter comprising:
a first waveguide having an output nanocoupler and an input nanocoupler oriented with a first incident polarization at a first angle;
a second waveguide having an output nanocoupler and an input nanocoupler oriented with a second incident polarization at a second angle;
2. The device of claim 1, wherein the first waveguide and the second waveguide conduct different energy levels depending on the polarization angle of incident polarization. the nanocircuit comprises a resonant waveguide network;
said resonant waveguide network comprising a plurality of waveguides, each of said plurality of waveguides having a nanocoupler at each end of said waveguide;
at least one of said nanocouplers configured as an input nanocoupler for receiving optical energy from an optical fiber and a plurality of other nanocouplers configured as output nanocouplers;
2. The device of claim 1, wherein the waveguide produces multiple resonances due to coherent interference of plasmon waves passing through the waveguide. 15. The device of claim 14, wherein the emission of light energy through said output nanocoupler depends on the frequency of light incident on said input nanocoupler. the nanocircuit comprises a plasmonic waveguide sensor;
The at least one waveguide comprises an input nanocoupler and an end, the end reflecting plasmonic energy in the waveguide and at least a portion of the reflected plasmonic energy returning to the optical fiber. 3. The device of claim 1, wherein the device is converted to light energy. providing a faceted optical fiber;
depositing a metal layer on the facet;
milling slots in a metal layer on the facet to form a waveguide;
milling a nanocoupler into the metal layer on the facet and configured to directly couple optical energy from the optical fiber with plasmonic energy in the waveguide. depositing a dielectric layer on the metal layer;
depositing a transparent conducting oxide layer on the dielectric layer; applying a bias to cause resonance of the dielectric layer and the transparent conducting oxide layer to modulate the phase and amplitude of the nanocircuit; 18. The method of claim 17, further comprising: varying. 18. The method of claim 17, further comprising depositing a transparent conductive oxide layer over said metal layer. 18. The method of claim 17, wherein milling comprises using at least one of focused ion beam machining and electron beam lithography.

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